<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <!-- 引入 vue.js 文件 -->
    <script src="../js/vue.js"></script>
</head>

<body>
    <div id="app">
        <span v-if="isUser">
            <!-- label for里面的 username 和input里面id的username 一样的话就是焦点绑定 -->
            <label for="username">用户账号</label>
            <input type="text" id="username" placeholder="用户账号" key="username">
        </span>
        <span v-else="isUser">
            <label for="usernames">用户邮箱</label>
            <input type="text" id="usernames" placeholder="用户邮箱" key="usernames">
        </span>
        <button @click="btn">切换类型</button>
    </div>
    <script>
        new Vue({
            el: "#app",
            data: {
                message: "Hello Vue",
                isUser: true
            },
            methods: {
                btn() {
                    this.isUser = !this.isUser;
                }
            }
        });
    </script>
</body>

</html>